Evaluation of survival and release of encapsulated bacteria in ex vivo porcine gastrointestinal contents using a green fluorescent protein gene-labelled E. coli

A gfp-labelled E. coli strain K 12 was used to study the survival and release of calcium alginate encapsulated bacteria in ex vivo porcine intestinal contents. Encapsulated bacteria survived better in ex vivo porcine gastric conditions compared to non-encapsulated free bacterial cells. There was 2 log decrease in viable cells of encapsulated E. coli GFP⁺ after 3 h incubation in gastric contents compared to 4 log decrease in the free non-encapsulated cells. There was a complete release of encapsulated bacteria (E. coli GFP⁺) within 1 h of incubation in small intestinal contents at 37°C, while it took 8 h to nearly completely release the encapsulated bacteria in colon content under similar conditions. There was only a partial release of encapsulated bacteria incubated in duodenal content even after 10 h of incubation. Using gfp labelled E. coli, the efficacy of alginate capsule in protecting the bacterial cells from gastric environment and releasing the encapsulated bacteria in the intestine (desired site) was demonstrated.